Synchronous speed-indicator.



A. E. GRIFFIN.

SYNGHRONOUS SPEED INDICATOR.

APPLICATION FILED MAR. 13, 1905.

904,693. Patented Nov. 24, 1908.

3 BHEETS-SHEET 1.

Wfnesses. [m/enfozr A. E. GRIFFIN.

SYNGHRONOUS SPEED INDICATOR.

APPLIOATION FILED MAR.13, 1905.

Patented Nov.24,1908.

38HEETS-SHEET 2.

ag z sggn 5 v 3/ A. E. GRIPFIN. SYNCHRONOUS SPEED INDICATOR. APPLIbATIONTILED MAR. 13, 1905.

Patented Nov. 24, 1908.

8 SHEETS-SHEET 3.

UNITED STATES "PA ENT OFFICE. I

ARTHUR EUGENE GRIFFIN, OF WINTHROP, MASSACHUSETTS, ASSIGNOR TO SEARS B.CONDIT, JR, OF BOSTON,MASSAOHUSETTS.

svncnnonous SPEED-INDICATOR.

Specification of Letters IPatent.

Patented Nov. 24, 1908.

Application filed limit 13, 1905. Serial No. 249,766.

' To all whom it may concern:

ings, is a specification, like letters on the drawin s representing likeparts.

My invention is an apparatus for indicating to the operator at theswitch board or elsewhere when a given machine has reached a synchronouscondition with relation to an alternating electrical circuit.

While my invention has a broad, general application in the electricalart, it is particularly adapted for use in connection with synchronizinginduction motors, and accordingly I will avail myseltof thisillustration to make my invention clearly understood.

When it is desired to connect into the main line, one or more largeinduction motors withoutv the danger of seriously disturbing the line,it. becomes necessary to syhchronizc the speed of the motor withrelation to the current in the main line, and man devices and systemshave been attemptec for accomplishing this result.

My invention is an indicating apparatus to enable the operator todetermine the proper moment for connecting the motor into the main line.

One ot mymain objects is to provide indicating means which can bemounted on the switch board, or at any remote )osition if desired, toenable a single attenc ant to determine, simply by observing theindicator, the exact instant when the motor is in perfeet synchronis'mwith the line current; and,

to this end, my invention has certain distinc-' tive requirements. Iprovide a make-andbreak device mounted on a moving part ot the motor,preferably on the rotor, and

connect the same in series with an indicating device in a circuit tappedfrom the main line beyond the main switch e. the main switch is betweenthe taps and the motor), so that no attention is required except the oneman to view the indicator located at or near the main switch.

in the simplest form (fi my invention I employ an indicator inconnection simply with the circuit tapped from the main line to themake-and-break device, and in such case the indicator is of that typewhich indicates direction of current and relative strength, such forinstance as a direct current volt meter or ammeter. Under thesecircumstances I prefer to employ a controlling switch forsaid shuntcircuit between the indicator and main line for giving initial certaintyof operation and producing sensitive indicating. Undersome'circumstances, however, it is desirable to employ an indicator ofthat type which is dependent upon two alternating electromotive torcesderived from separate sources (such for instance as a synchroscope oralternating current volt meter, or incandescent lamps), in which case Iconnect one side of the indicator with the circuit tapped as before fromthe main line and connect. the other side of the indicator with aninduced alternating current circuit derived from a pulsating directcurrent. The make-and-break device is arranged the same as before andacts to produce the pulsations required, and the induced alternationsmay be produced by any suitable induction device, preferably atransformer or reactive coil, so that when the frequency of said inducedcurrent becomes the same as that of the main line, and the waves of bothsources have thesame characteristics, as shown by the indicator, themotor is then running at synchronous speed with the main line, and theattendant thereupon closes the main switch to throw the motor intocircuit with the main line.

The further details of my invention and more explicit explanationthereof will be given in connection with the accompanying drawings, inwhich I have illustrated various features and preferred embodiments ofmy invention.

In the drawings, Figure l is a view mainly diagrammatic, showing thesimplest form of my invention, operating directly from the main linecircuit only; Fig. 2 is a perspective detail of the make-and-breakfeature of my apparatus; Fig. 3 is a view similar to Fig. 1 showing myinvention adapted. to operate in connection with the second type ofindicator above mentioned; Fig. 4 shows the latter construction in amore complete embodiment; Fig. 5 shows this form of my invention forindicating at the switch board in connection with any of a plurality ofmotors throughout the plant; and Fig. 6 isa diagrammntic view showingthis application of motor Mounted on the motor 1, to be operated T byany movable-portion thereof, is a makeand-break, device 6 for producingpulsations, herein shown as consistlng of a commutatorlike ring mountedon the rotor shaft 7 of the motor and having insulatin blocks 8 embeddedin said ring at equa? distances apart dividing the ring into manycontact blocks as there are pairs of poles on the motor. Cotiperatingwith this make-andbreak device 6 is a brush 9 carried by a bracket 10rigidly and referably adjustably secured to the frame 0 the motor.

Tapped from the main line are wires 11, 12, a step down transformer 13being. preferably interposed for convenience of manipulation and safetyto the indicator 14 which is interposed in series with one of thesewires, herein shown as in the wire 12. Preferably also a switch 15 isinterposed between said indicator and the main line. The indicator 1 1may be a volt meter, ammeter, or any of the well known forms of devicescapable of indicating the direction and strength of current flowingthrough it.

Let it be supposed that the parts are in the condition indicated inFig. 1. If, now, the motor 1 be started by the auxiliary power derivedfrom an independent source, as 16, and brought up ap roximatel -toproper speed, the operator t ereupon c oses the switch 15 therebycompleting the shunt circuit 11, 12. As long as the ulsations set up bythe make-and-break devlce 6 is difi'erent from the frequency of the mainline, the indicator 14 will be in constant motion, but as soon as thepulsations at the make-andbreak device correspond to the frequency inthe main line, the pointer of the indicator 14: will give a steadydeflection, thereby showin synchronous speed between the rotor o themotor 1 and the rotating field thereof or main line current. As thecontact spaces of the malte-and-break deviceceases its circuit will becompleted at ditlercntv points of the wave of the main line current, butthe moment that the said synchronous condition is reached, the indicatorwill remain steady because the successive con-- tacts of themake-and-break device will close or the circuit invariably at the samepoints of the wave of the main line current. Hence when the indicatorgives a steady deflection, the operator instantly closes the main switch3 -without danger of improper disturbance in the main line.

To adapt my invention toa wider range of indicators, such as thesynchroscope and Lincoln synchronizer, I connect such an alternatingcurrent synchronizing indicator 17 on one side to the tap circuit 11,12, as before, and connect it on the. other side to wires 18, 19 fromone side of a proper induction device, herein shown as a transformer 20,whose opposite Winding is in series with the make-and-break device 6 anda source of direct current 21 through conductors 22, 23, 24, a switch 25being interposed in the wire 23. As thus embodied, the operator, havinstarted themotor as before,

make-and-break device 6 imparts to the transformer 20 a series ofpulsations which are transformed into a corresponding series ofalternations for affecting the indicator in conjunction with thealternations of the tap circuit. 11, 12. The one series of alternationsis taken from the main line, while the other series is derived from theinductive from an independent direct current source. This enables me toshow not only the moment of synchronous speed, but also the relativespeed of the motor as compared with the frequency. of the main line.

If the direct current circuit were left closed with an uninterruptedcurrent, it would burn out the inductive coil or transthe switch 25.Also, to guard against improper closing of tlns switch, I provide anauxiliary contact 26, see Fig. 1, on the startstarting motor 5, in whichcase it will be understood that the direct current is supposed to bederived from the same source as the auxiliary motor circuit 16. In someinstances there is danger even yet of injury to the transformer 20, asfor example in case the field of the starting motor has too greatinitial strength, or for other reason the mo tor is slow, andaccordingly I interpose an automatic cut out across the direct currentthen closes the switch 25, whereupon thecoil or transformer 20 affectedby pulsations I former and hence it is necessary to provide ing rheostatswitch 27 of the auxiliary lilo circuit to the transformer, as indicatedat 28 Fig. 4 and shown more fully in connection with the completerepresentation of all features of my invention, as to this type,contained in Fig. 6. 'This cut out or automatic transformer-protectoroperates to cut out the transformer at ali times when the motor isrunning below speed.

Referring to Fig. 6, it will be seen that I have introduced a solenoid29 in shunt across the direct current side of the transformer 20, saidsolenoid however also having a circult-connection 30 to the oppositeterminal 24 from the make-and-break 6,the lattercircuit however beingnormally broken and only completed when the motor 1 has reachedsufficient speed for safety to the transformer.

The solenoid 29 connects at one end to the.

wire 22 by a conductor 31 and at its other end by a wire 32 to theconductor 2-31 In the wire 30 is a switch 33, operated by the movementof a core 34 of the solenoid 29, and a solenoid 35 whose core 36 0 ratesa circuit closer 37 rendered sluggish in action by any suitable means asa dashpot 38. The switch 33, as herein shown, has a movable memberprovided at its middle with a transverse portion 39 of conductivematerial and opposite end portions 41 of insulating material, saidmovable memberv operating between opposite spring contacts 40. Thecentral part 39 provides a contact-making area, and the insulation parts41 at the ends provide cut-out portions. It will be I understood that,except as otherwise expressed in certain of my claims, any otherautomatic switch and circuit-closer mechanism may be employed, theelectromagnettype herein shown bei usually preferable.

From the foregoing escription it will be understood that as themake-and-hreok device 6 revolves slowly at first, the current in thecircuit 22, 24 reaches a maximum value each time the circuit is closedand then declines to zero as the circuit is broken,- but as the speedincreases, thereby increasing the frequency of the interruptions, it isaccompamed by a decrease in current, due to the -1ncreased interruptionand also to the impedence of the circuit which includes the coil 29, sothat when the strength of current becomes just merely sufficient to beofi'set by the stren h of the spring 42, it maintains the switc 33closed, thereby operating the circuit closer 37 and permitting thecircuit 22, 23, 24 to operate with safety to the trans former. Whenthemake-and-break device 6 is moving slowly, it causes the movablecontact maker of the switch 33 to have a long range of movement, but themomentary closing of the switch thereby does not serve to operate thecircuit closer because of the dashpot 38 which prevents the latter fromoperatmg unless the contact 39 of the switch is held in closed positionfor an appreciable time.

And as the latter condition cannot take place until the uspeed of theinduction motor has become 5 cient to operate the transformer circuitwith safety, it follows that the transformer is effectually-protected bythe aforesaid mechanism under all conditions.

It being remembered that one of the principal objects of my invention isto enable the attendant at the switch board to control the cutting in ofthe individual induction motors throughout the facto or power plant, itbecomes necessary to a apt my invention to a selective system.

' Referring to Figs. 5 and 6 (Fi 5 showing the selective system simplyan Fig. 6 the complete embodiment of the entire apparatus) it will beseen that I have interposed in the transformer circuit wires 22, 23 aselector 43, it being understood that any convenient form of thisapparatus may be used, a usual dial switch being herein shown for thepurpose, in which a centrally pivoted arm 44 carrying contacts connectsat one end with sector contacts 45, 46 and atthe other end with pairs ofcontacts for connecting up u the respective induction motors AL, B andso on according to the requirements of the given factory, at third setof wires C being indicated in Fig. 5 for a third motor (not shown).

B means of the foregoing mechanism. it readily may be understood thatthe operator at the switch board simply turns the selective switch lever44 to the contacts for any given. motor, as A, and as soon astheindicator 17 notifies him that the motor has reached proper speed,hethrows the switch 3 of that motor, and then shifts the switch lever 44to the next motor B. As soon as the latter has reached proper speed, asshown by the indicator 17 he cuts it into the main line, and so onthroughout the entire factory, my inver. tion enabling the attendant todetermine accurately, without leaving the switch board,

the proper moment for cutting in any motor at any place in the system.

The operation of my mechanism has at ready been set forth in connectionwith the description and may,-therefore, he summarized briefly.

The main switch 3 being open, as usual,

the attendant watches until the induction motor 1 has attained. somespeed, whereupon he throws in the switch 15, Fig. 1, or the switch 25(Figs. 3 and 4) or 43 Figs. and 6) in the other embodiments of myinvention, and thereafter simply watches the indicator 14 or 17 as thecase may be. In the simpler form, as shown in Fig. 1, the indicatorsimply moves back and forth as the makeand-break device 6 rotates, untilthe speed of the make-and-break device is synchronous with the maincurrent, whereupon the indicator remains steady and the attendant 15thereby notified that the time has arrived for throwing in the mainswitch. Substan- &

tially the same operation takes places in connection with the indicator17, excepting that in addition to simply indicating whether the momentof synchronism has arrived, it indicates whether the motor is above orbelow synchronous speed; and to accomplish this result I have used thedirect current for operating in connection with the make-andbreakdevice, transforming the pulsations of msaid current into alternatingcurrent by means of the transformer 20 although any other means ofconverting the direct current into alternating current may be employed.The frequency of said transformer current depends upon the speed of themake-andbreak or pulsation-producing device 6. In this formof my devicethe operator, after the motor has attained some speed, throws- 'in theswitch 25, or the corresponding switch 43 of the selective system,thereby guarding against usual danger; and in the most completeembodiment of my invention, as shownin Fig. 6-, all danger is guardedagainst by the automatic transformer protector, so that it becomesimmaterial when the circuit of the make-and-break device is closed.

It has been my endeavor to simplify the embodiment of my invention sofar as possible so as to employ forthe different parts thereof wellknown'mechanisms, but it will be understoodthat various other mechanismsmay be substituted and many changes .may be resorted to'withoutdeparting from Y the spirit and scope of my invention, as

hereinafter expressed in the claims. Having described my invention, whatI claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The combination, with an induction motor, a source of alternatingcurrent therefor, and a source of direct current, of speed indicatingmeans'responsiveto alternating current, means for mfiuencin saidindicating means from said source or alternating current, and means,including a converter for said direct current operated by said motor,for likewise influencing said indicating means. I

5o 2. The combination, with aninduction motor, a source of alternatingcurrent therefor, and a source of direct current, of means visuallyresponsive to current alternations, connections from said means to saidsource of alternating current, and connections from said means to saidsource of direct current, including means for converting the lattercurrent into alternating current having the same periodicity as saidmotor.

'60 3. The combination, with an induction motor, and its feed wires, andmain switch, of a make-and-breakdevice mounted thereon to be operated bya moving part of said motor, and a synchronous speed-mdicator, included6 in a circuit from said make-and-break device and from said feed wiresbeyond the main switch, and governed by the alternations derived bothfrom the main line source of current and from said make-andehreakdevice.

4. The combination, with an induction motor, its feed wires, and mainswitch, of a make-and-break device mounted thereon to be operated by amoving part of said motor, a synchronous speed-ind1cator,means tappedfrom the main line for transmittin alternating current therefrom to saidin icator, and means for transmitting induced current to said indicatorfrom said make-and-break device.

5. The combination, with an induction motor, its feed wires, and mainswitch, of a make-and-break device mounted thereon to be operated by amovin part of said motor, a synchronous speed-in icator, means tappedfrom the main line for transmitting alter- 5 n'ating current therefromto said indicator, and means for transmittm induced current .to saidindicator from sai 'make-and-break device, said latter means including adirect current circuit and a transformer operated thereby.

6. The combination, with an induction mo-- tor, its feed wires, and mainswitch, of a make-and-break device mounted thereon to be operated by amoving part of said motor, a synchronous speed-indicator, means ta pedfrom the main line for transmitting a ternating current therefrom tosaid indicator, and means for transmlttin induced current to saidindicator from sai make-and-break device, said latter means including adirect current circuit and a transformer operated thereby, and a handswitch for governing said dlrect current circuit.

7. The combination, with an induction motor, its feed wires, and mainswitch, of a make-and-break device mounted thereon to be operated by amoving part of said motor I a synchronous speed-indicator, means tappedfrom the main line for transmitting alternating current therefrom tosaid indicator, means for transmittin induced current to said indicatorfrom sai make-and-break device, said latter means including, a directcurrent circuit and a transformer o erated 115 thereby, and an.automatic protector or said transformer maintaining tne latterinoperative untilthe motor has reached normal speed.

8, The combination, with a plurality of independent induction motors andtheir re"- spective switches and feed wires, of a makeand-break devicefor each motor, a synchronous spced-indicator, and'selective means forcoupling said indicator in circuit with the 12 make-and-break device ofany given motor and the feed wires thereof.

9. The combination, with an inducjtion motor, a source of alternatingcurrent therefor, and a source of direct current, fof speed-indi= 13motor, a source of alternating current there for, and a source of directcurrent, of speedindicating means responsive to alternating current,means for influencing said indicating means from said source ofalternating current, andmeans, including an inductive coil for saiddirect current, pulsated by said motor, likewise influencing saidindicating means, and a protective switch in the circuit including saidcoil and said source of direct current.

In testimony whereof, I have signed my 20 nameto this specification, inthe presence of two subscribing Witnesses.

ARTHUR EUGENE GRIFFIN. Witnesses:

Geo. H. MAXWELL, M. A. J oNEs.

